1. Field of the Invention
The invention relates to cutter blades for the production of gears and, more particularly, to cutter blades for the face hobbing of parallel depth spiral bevel and hypoid gears.
2. Description of the Prior Art
Spiral bevel and hypoid gear pairs are conventionally produced utilizing either an intermittent index face milling method or a continuous indexing face hobbing method. While most gear set manufacturers currently use the face milling method, the face hobbing process has been recently adopted by some manufacturers, especially those manufacturing such gear sets for vehicular applications. In a face hobbing machine, a circular face hob type rotary cutter carrying a plurality of cutter blades mounted in groups, is utilized, and a workpiece (gear blank) and the cutter continuously rotate in a timed relationship until the entire part is completed. During the cutting process, the workpiece indexes in a rotary manner so that each successive cutter blade groups engaging successive tooth slots as the gear or pinion member is being cut. Advantageously, the face hobbing method produces uniform depth teeth, and parts are produced from the solid in one operation. The face hobbing method also requires fewer production steps and less production time than the face milling method.
Normally, in an operation separate from, and preceding to, the tooth cutting operation, a topland surface of the gear is machined while processing a ring gear or pinion gear blank before cutting the gear teeth. As well known to those skilled in the art, the additional production step is generally disadvantageous with regard to cost, labor, quality control, and manufacturing flexibility.
The present invention relates to a gear cutter blade for use with a face hob type cutter for producing teeth of spiral bevel and hypoid gear members by a continuous index, face hobbing process. The gear cutter blade comprises a cutter blade shank adapted to be mounted on a rotatable cutter body, and a cutting member provided at one end of the blade shank. The cutting member includes a tooth side cutting edge having a given axial pressure angle, and a topland cutting edge adjacent the tooth side cutting edge. The topland cutting edge of the cutting member simultaneously forms a topland surface of the tooth of the gear member as a tooth side surface is cut by the tooth side cutting edge of the cutting member.
Machining the topland surface simultaneously with the cutting the tooth side surface permits to reduce or completely eliminate the need to finish topland surfaces of the ring gears or pinions. Moreover, the elimination of a subsequent manufacturing operation improves the consistency and accuracy of the gear tooth whole depth, and part quality, as well as reduces manufacturing costs. In addition, the gear cutter blade of the present invention allows for greater manufacturing flexibility, as the cutting edge dimensions can be easily modified, and provides an ability to machine near-net forged parts without requiring precision control of the topland area of machining with an interrupted cut during a blanking operation.